Line of Position (LOP) (LOP)

A line on which an observer’s position must lie according to one measured bearing, range, angle or other observation.

Examples include a bearing line to a charted object, a radar range circle, a depth contour under suitable conditions or a celestial position line. Two independent LOPs may intersect at a fix, while three can reveal inconsistency as a cocked hat.

Accuracy depends on object identification, geometry, timing, instrument and plotting error. LOPs taken at different times require allowance for vessel movement before they are combined.